Condensation on your windows: what it means and what to do
Condensation on windows is moisture from the air landing on the coldest surface in the room. The glass is usually the coldest thing there, so it's the first place to show it. Misting on the inside of the glass on a cold morning is common. Water running down the window every day, or mould growing on the frame and the wall beside it, is a sign the air is too damp for the room.
Why it forms
Every day a home makes a lot of water vapour. Cooking, washing, showering, breathing and drying clothes all put moisture into the air. Warm air holds more of it, and when that air touches a cold surface, the moisture turns to water. In winter, when the heating is on and the windows are shut, that process happens faster and in more places.
Windows are more likely to show it if they are single-glazed, if the room is cold, or if the air isn't moving. Kitchens, bathrooms and bedrooms are the usual places, because that's where the most moisture is made or where people spend the night.
What you can do this week
The fix is mostly about moving the moisture out and keeping the room warm enough that the glass isn't the coldest thing in it.
- Run the extractor fan, or open a window, while you cook, shower and bath. Keep it going for a while afterwards.
- Open a window for a few minutes, a few times a day, rather than leaving it open all day.
- Dry washing outside if you can, or in a room with the window open and the door shut. Drying it on radiators adds a lot of moisture to the air.
- Wipe the condensation off in the morning, and dry the window sill. Leaving it to soak in makes mould more likely.
- Keep the room at a steady warmth, rather than letting it go cold and then heating it fast. A cold room with wet air is the worst combination.
- Check that trickle vents, where fitted, are open and not blocked by curtains or furniture.
- If the bottom of your curtains has gone mouldy, our guide to mould on clothes and curtains explains how to clean them and keep them dry.
When it's more than condensation
If the water is coming from inside the glass or the frame, or the window seals have failed, the problem is the window itself, and a glazier or window firm needs to look at it. A stain on the wall below the window that grows after rain can mean water is getting in around the frame, so check the outside too.
Mould on the frame, the reveal or the wall around the window is condensation mould in most homes. It can be cleaned, but it will come back while the window stays cold and the air stays damp. If you see staining that doesn't follow the weather, or a damp smell that never really goes away, get it checked for a leak.
Your health
The NHS says mould can trigger asthma in people who are allergic to it. If there is mould on or around the windows in a room where someone with asthma or a mould allergy sleeps or sits, it's worth cleaning it and dealing with the cause sooner rather than later. The NHS asthma causes page has more on the triggers. Official guidance for rented housing in England, Damp and mould: understanding and addressing the health risks for rented housing providers from MHCLG, DHSC and UKHSA, says anyone can be affected, and that people with asthma or allergies, children and older people are among those at greater risk. Speak to your GP if symptoms get worse.
When to get a specialist
Get help if the condensation is heavy every morning, the mould keeps coming back, or it has spread beyond the window area. Tell us what's happening and we'll pass it to one independent specialist who covers your area. They can look at the ventilation and the cause, not just the mould. It's free to ask.
If you rent: tell your landlord about condensation and mould in writing, with photos and dates. Our tenants' guide explains what they should do next and where to get help if they don't respond.
If you're a landlord: a tenant reporting condensation may be reporting a damp problem under Awaab's Law in Scotland, so the deadlines can apply. Our landlords page explains the rules, and the deadline calculator works out the dates.
Last checked 26 October 2026. This is general guidance, not legal or building advice.
Common questions
Is condensation on windows normal?
Yes, in the cold months it's common, especially in kitchens, bathrooms and bedrooms. It becomes a problem when it's heavy, runs down the glass every day, or leaves mould on the frame or the wall around it.
Should I open the window to get rid of it?
Opening a window for a while, even in winter, lets damp air out. Doing it briefly and often works better than leaving a window open all day, which can make the room cold enough for condensation to form elsewhere.
Are double glazing and condensation linked?
Old single glazing is colder, so condensation forms on it more easily. Better glazing helps, but it doesn't stop the moisture being made in the first place, so ventilation still matters.
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This is a free matching service, not the firm doing the work. We pass your details to one independent damp and mould specialist who covers your postcode. They contact you, arrange a visit and quote you directly. You don't pay us anything.